1. Field of the Invention
The present invention relates to isolated polypeptides having amylolytic enhancing activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.
2. Description of the Related Art
Starch is a complex carbohydrate composed of two main components: amylopectin and amylose. Amylose is a straight chain molecule while amylopectin is a branched molecule. Amylose is composed of D-glucose molecules that are linked by alpha-1,4-glycosidic bonds. Amyopectin is composed of D-glucose molecules that are linked by alpha-1,4-glycosidic bonds as well as D-glucose molecules linked by alpha-1,6-glycosidic bonds. The alpha-1,6-glycosidic linkages give rise to branching. The ratio of amylose to amylopectin varies among sources of starch.
Starch can be hydrolyzed into simpler carbohydrates by acids, various enzymes, or a combination thereof. The extent of conversion is typically quantified by dextrose equivalency (DE), which relates to the fraction of the glycoside bonds in starch that have been cleaved. The primary enzymes used to hydrolyze starch into simpler carbohydrates are endoamylases, exoamylases, and debranching enzymes, which hydrolyze amylose and amylopectin. Amylose is hydrolyzed mainly by amylases, while amylopectin also requires debranching enzymes such as pullulanases (E.C. 3.2.1.41) for complete hydrolysis. The endoamylases, the most common being alpha-amylase (E.C. 3.2.1.1), are specific for alpha-1,4-linkages of amylose and amylopectin. Exoamylases have the ability to hydrolyze both alpha-1,4-linkages and alpha-1,6-linkages of amylose and amylopectin. A common example is amyloglucosidase (E.C. 3.2.1.20). Beta-amylase is an enzyme that has the ability to hydrolyze the alpha-1,4-linkages of amylose. Debranching enzymes, e.g., pullulanases, hydrolyze alpha-1,6-linkages in amylopectin. Hydrolysis products of debranching enzymes are mainly maltotriose and maltose.
There are many food products that are produced from starch, which include, for example, maltodextrin, a lightly hydrolyzed (DE 10-20) starch product used as a bland-tasting filler and thickener; various corn syrups (DE 30-70), viscous solutions used as sweeteners and thickeners in many kinds of processed foods; dextrose (DE 100), commercial glucose, prepared by the complete hydrolysis of starch; and high fructose syrup, made by treating dextrose solutions with the enzyme glucose (xylose) isomerase, until a substantial fraction of the glucose has been converted to fructose.
It would be advantageous in the art to improve the enzymatic conversion of starch-containing materials.
The present invention provides isolated polypeptides having amylolytic enhancing activity and polynucleotides encoding the polypeptides and processes for their use.